Three-step clearance control



' 1,616,987 1927' v w. PRELLWITZ THREE-STEP CLEARANCE CONTROL Filed Aug. 4, 1926' IN V EN TOR.

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Patented Feb. 8, 19 27.- UNITED, STATES PATENT 'orrlc WILLIAM PRELLWITZ, OF EASTON, PENNSYLVANIA A SSIGNOR TO INGERSOLL-RAND COMPANY, OF JERSEY CITY, JERSEY, A CORPORATION OF NEW- JERSEY.

THREE-STEP CLEARANCE CONTROL;

Application filed Auggst 4, 1926. Serial m. 127,059.

This invention relates to compressor unloaders, but more particularly to a clearance unloader which unloads and loads in three steps, that is, full load, half load and no load, considering the full loadcondition as one of the three steps. j

The object of the invention is to enable a compressor to be unloaded entirely by clearance chambers, but in few steps and throughout each step pressure at each end of the cylinder is substantially the; same and the compressor is maintained in balanced condition.

The invention is illustrated in one of its preferred forms in the accompanying drawing which is a diagrammatic representation partly ,in longitudinal section of a simple unloadin system.

Referring to the drawings, the cylinder A 0 having the piston B receives air through the intake C and discharges it through the dis charge outlet D to the receiver E, The cylinder is provided with four clearance chambers F,'G, H and J, so that by opening the chambers F and G. simultaneously at opposite ends of the cylinder, the compressor is half unloaded in one step and by opening the chambers H and .J simultaneously at opposite ends of the cylinder, the compressor runs under no loadias the final step.

The compressor has the usual inlet and discharge valves K and L which may be of the plate type. The clearance chambers are provided withthe. clearance valves 0, P, Q, and R and valved ening mechanism comprising the pistons operating in the cylinders T and having the retracting springs U. The regulationfiseffected by a suitable regulator and a simplet e of regulator is 4 shown comprising a cylin er V. having-Lethe piston W which. is subjected to receiver pressure at oneend through'the pipe Xand is provided with 'an' adjustable retracting sprlngY at the other end. The piston is 15 cut away at a to cooperate with the ports I) and c in the cylinder V. Pipes 1 joining together and leading froin-the port I), sup-' ply pressure to thegcylinders T of the clear- 'ance valves 0 and P, while i ing' togetherandleading from the port a, supply pressure to .thecylinders T of the clearance valvesQ and R.

, ,In theoperationof the device',.iwhen-.the piston'Wof the regulator is moved'the first step to the left as the figure is viewed, then I pipes 2 join the port 6 is uncovered and subjected to re- 1. In a compressor unloader, the combination of a cylinder and piston, inlet and nation of a cylinder and piston, inlet and discharge valves, a receiver, tW.o clearance chambers and clcaran'cevalves for each end of the cylinder, and means for operating the clearance chambers in successive-pairs, to first partially unload the compressor and then wholly unload'the compressor.

3. In a compressor unloader, the combination of a cylinder and p1ston, 1nlet and chscharge valves, a receiver, two clearance chambers and clearance valves for each end of the cylinder, and automatic means responsive to receiver pressure for operating the clearance valves in successive pairs, to first partially unload the compressor and then wholly unload the compressor, thereby keeping the compressor balanced.

4 In a compressor unloader, the combi-- nation of acylinder and .piston, inlet and discharge valves, a receiver, two clearance chambers and clearance valves for each end of the cylinder, and automatic means responsive to receiver pressure for operating the clearance valves in successive pairs, the

valves of each pair being located at opp0-.

site'ends'of the cylinder, for efiecting steps of unloading, thereby keeping the pressures at each end of the cylinder substantially the same and maintaining a balanced condition in the compressor.

In testimony whereof I- have signed this specification;

WILLIAM PBELLWITZ 

